Abstract
The function of the vertebrate nervous system is based on
the rapid and accurate transmission of electrical impulses. The
myelin sheath is a lipid-rich membrane that envelops the axon, preventing the
leakage of the nervous impulse to the environment. Myelin is formed
when the plasma membrane of a myelinating glial cell differentiates
and wraps around an axon. The compaction of myelin leads to the
extrusion of most of the glial cell cytoplasm from the structure.
Both the compact and noncompact regions of myelin carry distinct
subsets of proteins.
The myelin-associated glycoprotein (MAG) is present in noncompact
myelin. It is a cell adhesion molecule expressed only by myelinating
glial cells. Two isoforms of MAG, S- and L-MAG, exist, and these
forms differ from each other only by their cytoplasmic domains.
Until now, little information has been available on the differences
between the MAG isoforms. This study was carried out in order to
gain information on the cytoplasmic domains of S- and L-MAG.
Significant differences were observed in the properties of
the MAG cytoplasmic domains. An interaction between the L-MAG cytoplasmic
domain and the S100b protein was characterised, and a role for this
interaction was found in the regulation of L-MAG phosphorylation.
Evidence was also obtained for the dimerisation of the L-MAG cytoplasmic
domain. The S-MAG cytoplasmic domain bound zinc, which induced a
change in the surface properties of the protein. The S-MAG cytoplasmic domain
was also found to interact directly with tubulin, the core component
of microtubules.
In conclusion, this study has brought information on the functions
of the MAG cytoplasmic domains. The results are complementary with
ealier hypotheses on the roles of the MAG isoforms in myelinating
glia. While the properties of L-MAG suggest a role as a signaling
molecule, a dynamic structural role for S-MAG during myelin formation
and maintenance can be envisaged.
| Identifer | oai:union.ndltd.org:oulo.fi/oai:oulu.fi:isbn951-42-5669-7 |
| Date | 23 May 2000 |
| Creators | Kursula, P. (Petri) |
| Publisher | University of Oulu |
| Source Sets | University of Oulu |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/doctoralThesis, info:eu-repo/semantics/publishedVersion |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess, © University of Oulu, 2000 |
| Relation | info:eu-repo/semantics/altIdentifier/pissn/0355-3221, info:eu-repo/semantics/altIdentifier/eissn/1796-2234 |
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